The difficulty of bonding textile fibers to rubber is manifest in the great difference between the two types of surfaces, and the necessity for a bond to exceed the strength of both substrates. The bond must have the ability to resist extremes of temperature, compression loads, shock, creep and distortion.
Textile-to-rubber adhesives are utilized extensively in automobile tire manufacture for bonding tire cord and other textile components to the rubber carcass. Other significant applications for textile-to-rubber adhesives are in the production of rubber belts, hose, rubberized fabrics and rugs.
Latex dips are employed for coating of fibers such as nylon, rayon, polyester and glass to improve the adhesion of the fibers to rubber substrates.
In the use of the many dips that have been developed, it is preferred to pretreat fibers with adhesive resorcinol-formaldehyde resin(RF) dip, or with RF dips containing a preparation of elastomeric latex (RFL dips), or with epoxy dips, and to dry the coated fibers before assembling with another substrate (e.g., a vulcanizable elastomer) and curing the composite for the purpose of providing a bond between the substrates.
The various adhesive latex formulations employed as dips for fiber coating do not exhibit the most desirable rheological properties for effecting an efficient fiber coating operation. The viscosity properties are variable, and the control of flow parameters is difficult.
A variety of thickeners have been incorporated in latex formulations for flow-regulation, such as those described in U.S. Pat. No. 3,779,970 and U.S. Pat. No. 4,341,674. A typical thickener suffers from one or more shortcomings, such as incompatibility with other latex formulation components, too high a viscosity during application, sensitivity to pH or temperature conditions, or slow viscosity recovery after high shear conditions, and the like.
There is continuing interest in the development of novel adhesive latex formulations with improved properties for the coating of substrates such as fibers for textile-to-rubber bonding.
Accordingly, it is an object of this invention to provide a novel flow-regulated latex system.
It is another object of this invention to provide a shear-thinning aqueous adhesive composition adapted for improved textile-rubber bonding efficiency.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.